This invention relates in general to a hydrokinetic torque converter assembly of the lockup clutch unit-equipped type for use in an automatic power transmission which is designed and constructed to be transversely mounted on a F-F type motor vehicle in which an engine such as an internal combustion engine is mounted at the front of the vehicle with the drive to the front wheels and, more particularly, to the improved fluid passage construction and arrangement for converter fluid supply and return circuits and a lockup control circuit incorporated in the hydrokinetic torque converter assembly of the above type.
In case of the F-F type motor vehicle having transversely mounted thereon an automatic power transmission, it is particularly desired to locate the final drive unit at the center of the vehicle, i.e. intermediate between the lateral sides of the vehicle body, so that the left and right axle shafts for respectively driving the left and right front wheels may have the same length. It is accordingly desired to locate the output gear of the power transmission as close as the possible to the center of the vehicle.
For this reason, it has been practiced to dispose the output gear immediately near the torque converter and the oil pump assembly of the power transmission in the transmission end portion far away from the torque converter. The pump drive shaft of the power transmission for driving the oil pump assembly is thus necessitated to be of a considerable length so as to extend throughout the ratio changing mechanism of the power transmission to drivingly interconnect the front converter cover of the power transmission and the oil pump assembly. The transmission input shaft employed in this type power transmission for transmitting the output of the torque converter to the ratio changing mechanism is constructed as a hollow shaft surrounding the pump drive shaft and is also necessitated to be of a considerable length as is well known in the art.
The hydrokinetic torque converter assembly of the lockup clutch unit-equipped type for the foregoing transverse automatic power transmission requires the provision of three kinds of fluid circuits including a converter fluid supply circuit, a converter fluid return circuit and a lockup control circuit. The converter fluid supply circuit is provided for supplying the converter working fluid from the source of fluid under pressure of the working circuit in the torque converter, and the converter fluid return circuit is provided for discharging the converter working fluid from the working circuit in the torque converter to the oil sump through the relief valve. The lockup control circuit is provided for alternatively actuating the lockup clutch unit into a lockup-applied condition or a lockup-released condition. The converter fluid supply circuit, the converter fluid return circuit and the lockup control circuit respectively includes a converter fluid supply passage, a converter fluid return passage and a lockup control passage which are necessary to be arranged between the concentrically disposed shafts of the torque converter.
Referring to FIG. 1 a hydrokinetic torque converter assembly of the foregoing type will be explained.
Reference numeral a indicates a pump drive shaft for driving an oil pump assembly, which is drivingly connected to a converter cover b driven by an engine. A transmission input shaft c surrounds the pump drive shaft a interposing therebetween a bushing d. The transmission input shaft c is drivingly connected to a turbine e and is journaled by means of a bushing g in the bore of a stationary sleeve shaft extension f of a cover member. The stationary sleeve shaft extension carries thereon a stator h by way of a one-way clutch assembly i and also carries thereon by way of a bushing j a pilot sleeve shaft 1 integrally connected to an impeller k. A lockup clutch unit is disposed in the converter cover b and includes a clutch piston m engageable with the converter cover b to rotate together therewith and a torsional damper assembly n interconnecting the clutch piston m and the turbine k.
Of the aforementioned three fluid passages, the lockup control fluid passage is defined by means of a central opening o formed in the pump drive shaft a, and the converter fluid supply passage is defined by means of an annular space p between the transmission input shaft c and the stationary sleeve shaft extension f and a radial bore q formed in the stationary sleeve shaft extension f. The converter fluid return passage is defined by means of an annular space s between the pump drive shaft a and the transmission input shaft c and a radial bore r formed in the transmission input shaft c.
The torque converter assembly thus constructed and arranged contours a drawback that the pump drive shaft a is inferior not only in mechanical strength but also in manufacturing cost since the central opening o is formed in the shafts a of a small cross section relative to its length. The prior art converter assembly is further undesirable in that the radial bore r is formed in the transmission input shaft c for transmitting a driving power, which inevitably deteriorates the mechanical strength of the transmission input shaft c.
It is accordingly an object of the present invention to provide a hydrokinetic torque converter assembly of the lockup clutch unit-equipped type which is improved to be free from the foregoing drawbacks in the torque converter assembly of the described type.
It is a further object of the present invention to provide a hydrokinetic torque converter assembly of the lockup clutch unit-equipped type in which the foregoing three fluid passages are constructed and arranged between the foregoing four concentrically disposed shafts without requiring the provision of an central opening in a pump drive shaft and a radial bore in a transmission input shaft.